1. Field of the Invention
The present invention relates generally to a method and apparatus for manufacturing a sensitized printing plate, and more particularly to a method and apparatus for cutting a sensitized printing plate, which can improve a printed matter, and the sensitized printing plate which is cut in the above-mentioned method and apparatus.
2. Description of Related Art
A sensitized printing plate is widely used as a pre-sensitized plate (PS plate). To manufacture the PS plate, surface treatment such as graining, anodic oxidation and chemical conversion coating are, singly or in combination, generally performed on the surface of a sheet-shaped or coil-shaped aluminum plate. Then, a sensitive solution is coated on the plate and the plate is dried, and the plate is cut into a desired size.
On the other hand, as an example of printing by means of the printing plate, which is made by image-sensitizing and developing the PS plate, a printing machine prints paper which is smaller than the printing plate, and paper which is wider than the printing plate as newspaper's printing. In the case of the latter, the both surfaces of the printing plate are used to be printed. For this reason, ink on a cut end of the printing plate is printed on the printed paper. As a result, a printed matter is ruined and its merchandise value can be lowered.
In order to prevent the printed paper from getting stained by the ink on the cut end of the printing plate, for example, Japanese Patent Publication No. 57-46754 has disclosed a method which files a corner of the end of the aluminum base plate with a file, a knife, etc., and Japanese Patent Publication No. 62-61946 has disclosed a method which coats an oil-insensitive solution on a cut surface.
In addition, Japanese Patent Provisional Publication No. 62-19315 has disclosed a method which prevents a burr from forming on the printing surface because the burr makes stains on the printed paper. Furthermore, Japanese Patent Provisional Publication No. 7-32758 has proposed that the cut end is bent to the reverse side of the printing surface, and Japanese Patent Application No. 8-192079 has disclosed a method which hangs the surface of the cut end on the reverse side of the printing surface, and roughs the side surface so as to decrease the stain of the printed paper.
However, the above-mentioned method, which shaves the corner of the end of the base plate with a file or a knife, is not suitable for a mass production. Moreover, a burr is cut, the ink may be put on the filed part, and thereby the ink can stain the printed paper. The method which coats the oil-insensitive solution on the cut surface also has a disadvantage because the printing plates stick to one another and the development cannot be satisfactorily carried out.
Even if the burr is prevented from forming on the printed paper during cutting, the surface is stained under some conditions. Although the stain on the cut end which is bent down (to the reverse side of the printing surface) can be decreased, it may get stuck while it is transferred in a printing machine which exposes an image.
Magenta ink, etc. can stain a sample a long time after the cutting. If a shear droop is formed on the cut end surface so as to prevent the stain caused by the ink, a surface layer extends, and a crack is generated on a sensitized layer and the surface of the sensitized printing plate.
Japanese Patent Provisional Publication No. 5-104872 discloses that the crack on a surface treatment layer causes the stain; however, the Patent Provisional Publication does not disclose about decreasing the stain caused by the crack among the frame-shaped stain on the printing surface of the plate.